1. Field of the Invention
The present invention relates to an industrial two-layer fabric, in particular, to an industrial two-layer fabric that is rigid, has water drainage properties, is wear resistance, has fiber supporting properties, has a papermaking yield, and high resiliency (lifespan).
2. Description of the Related Art
Fabrics made by weaving warps and wefts are used widely as industrial fabrics and in many other fields, for example, papermaking fabrics, conveying belts, and filter cloths, and these fabrics require fabric properties suited for those environments.
Requirements for papermaking fabrics used in a papermaking water removal step from raw materials by utilizing meshes of the fabrics are especially strict. For example, there is a demand for fabrics that do not easily transfer a wire mark of the fabrics to paper and are therefore superior in surface property, fabrics having a dehydration property to enable complete removal of excess water contained in the raw materials and being sufficiently rigid and wear resistant to enable suitable use of the fabric even under severe environments, and fabrics capable of retaining conditions necessary for making excellent paper for a long time period.
There is also a demand for fabrics having a fiber supporting property, capable of improving a papermaking yield, having size stability, having running stability, and the like. A higher demand for papermaking fabrics has developed from a recent increase in the speed of a papering machine.
Among industrial fabrics, papermaking fabrics must satisfy the most severe requirements so that a description of them will promote an understanding of these requirements and the solutions. Therefore, one example of the papermaking fabrics is described below.
In typical industrial fabrics, fabrics are traveled by joining the fabrics, which have been obtained by weaving to have ends, in an endless manner by the conventional method, suspending them in a plurality of rollers, and travelling the rollers while applying a tension thereto.
Since raw materials for making paper are supplied on the upper side layer of a papermaking fabric, the upper side layer is preferably dense, has a high supporting property, and has a surface smoothness. On the other hand, the lower side layer (the roller contact surface) is preferably excellent in wear resistance, rigidness, and has great water drainage properties. It is said that the upper side layer has preferably a design in which a predetermined pattern is repeated regularly, while the design of the lower side layer is still under investigation.
There are actually various designs proposed for the lower side layer. The fabric described in Japanese Patent Application Laid-Open No. 2006-152462 eliminates the defect of a ribbed weave design by forming a long crimp of lower side wefts and therefore has improved wear resistance. In this fabric, the float of lower side wefts can be made longer because although two adjacent warps have the same design as the ribbed weave design, they have each a design in which it passes under a lower side weft and then over a plurality of lower side wefts adjacent to each other.
However, this fabric also has a problem. Compared with the fabric of a ribbed weave design, this fabric has less weaving positions, which reduces its rigidness. In addition, wefts cannot be fixed firmly owing to a too long crimp of lower side wefts. As a result, the fabric's lifespan is not increased despite an increase in the wear volume of the wefts.
A fabric having improved rigidness is described in Japanese Patent Application Laid-Open No. 2006-57217. A lower side warp approaches the lower side warps adjacent to the right and left successively, and thus, are arranged in a zigzag manner so that the fabric has improved rigidness. But the undesirable movements of wefts cannot be prevented because the crimp is too long. Further, the fabric has undesirably increased in thickness.
A fabric having a crimp of an adequate length while maintaining rigidity is considered. The fabric has, as shown in FIG. 9 in Japanese Patent Application Laid-Open No. 2001-355191, an 8-shaft design in which a lower side weft passes over one lower side warp, under one lower side warp, over one lower side warp, and then under five successive lower side warps. When such a design is employed, the fabric has excellent rigidity because of an increase in weaving positions, is therefore firmly woven without undesirable movements of wefts, and has excellent wear resistance.